Cell cultures of neuronal cells will be used as model systems for neurochemical studies. Among the cells used are chick sympathetic neurons, a somatic cell hybrid line between mouse neuroblastoma cells and sympathetic ganglion cells and and a rat pheochromocytoma cell line. The various parameters to be studied will be a) regulation of acetylcholinesterase activity and of multiple forms of this enzyme; b) catecholamine metabolism (i.e.; synthesis, storage and release); c) mechanism of action of nerve growth factor; d) regulation of and mechanisms involved in neurite extension; e) cellular protein metabolism. BIBLIOGRAPHIC REFERENCES: Greene, L.A., Shain, W.; Chalazonitis, A.; Breakefield, X.; Minna, J.; Coon, H. and Nirenberg, M.: Neuronal properties of a somatic cell hybrid between mouse neuroblastoma and sympathetic ganglion cells. Proc. Nat. Acad. Sci., in press. 1975. Jacobowitz, D.M.; Greene, L.A. and Thoa, N.B.: Chromaffin Cells in Culture. (O. Eranko, Ed.), in press 1975.